1. Field of the Invention
The present invention generally relates to methods for forming metal line of semiconductor device, and more specifically, to methods for forming metal line of semiconductor device wherein via contact plug is formed without the deposition process of Ti/TiN liner layer and conductive layer filling a via contact hole so that the formation processes of a conductive layer for lower metal line and a conductive layer for via contact plug are performed successively without interruption to minimize the contact resistance between the lower metal line and the via contact plug, thereby simplifying the manufacturing process and improving productivity, characteristics and reliability of the device.
2. Description of the Prior Art
Generally, conductive lines of semiconductor devices used for electrical connection between devices and between a device and an external circuit is formed by filling a contact hole and via hole with conductive material and performing subsequent processes.
Metal lines are used where low resistance is required. Aluminum alloys, formed by adding silicon, copper or both of silicon and copper to aluminum, are used as materials for the metal lines for its low resistivity and excellent process characteristics.
FIGS. 1a through 1g are cross-sectional diagrams illustrating a conventional method for forming metal line of semiconductor device.
Referring to FIG. 1a, a lower metal line 11 is formed on a semiconductor substrate(not shown). The lower metal line 11 is an aluminum alloy film, and comprises Ti layers or Ti/TiN layers thereon and thereunder.
Thereafter, a planarized interlayer insulating film 13 formed on the entire surface. A photoresist film pattern 15 is then formed on the interlayer insulating film 13. The photoresist film pattern 15 is formed by exposure and development process using metal line contact mask(not shown) for forming a via contact hole.
Referring to FIG. 1b, the interlayer insulating film 13 is etched using the photoresist film pattern 15 as a mask to form a via contact hole 17 exposing the lower metal line 11. The photoresist film pattern 15 is then removed, and Ti/TiN liner layer 19, which is a bonding layer/diffusion barrier layer, is formed on the entire surface including the inner surface of the via contact hole 17.
Referring to FIG. 1c, a tungsten layer 21 filling the via contact hole 17 is formed on the entire surface.
Referring to FIG. 1d, the entire surface is planarized using the interlayer insulating film 13 as an etch stop layer to form a via contact plug 21 filling the via contact hole 17.
Referring to FIG. 1e, a conductive layer 23 for upper metal line is formed to be electrically connected to the via contact plug 21. The conductive layer 23 comprises a stacked structure of a lower Ti/TiN film, a main conductive layer for metal line, and an upper Ti/TiN film. The lower Ti/TiN film prevents the main conductive layer from reacting with the interlayer insulating film 13 which is a oxide film when the main conductive layer is an aluminum alloy or a tungsten alloy. The lower Ti/TiN film also allows uniform deposition of the aluminum alloy. The upper Ti/TiN film serves as an anti-reflective film and improves characteristics of electro-migration.
Referring to FIG. 1f, a photoresist film patter 25 is formed on the conductive layer 23. The photoresist film pattern 25 is formed by exposure and development process using an upper metal line mask(not shown).
Referring to FIG. 1g, the conductive layer 23 is etched using the photoresist film pattern 25 as a mask to form an upper metal line electrically connected to the lower metal line 11.
FIGS. 2a through 2c are SEM photographs illustrating a metal line manufactured in accordance with the conventional method.
FIG. 2a illustrates a multi-layer metal line. FIG. 2b illustrates a portion of the multi-layer metal line of FIG. 2a around the via contact plug, where seams are generated due to unstable deposition of the Ti/TiN liner film 19.
FIG. 2c illustrates the tungsten layer 21 poorly deposited on the unstable Ti/TiN liner film 19.
As described above, in the conventional method for manufacturing metal lines, seams generated during the formation process of via contact plug, poor quality tungsten film and high contact resistance degrades the characteristics of the device. Moreover, the manufacturing method is complex so that undesired impurities such as particles, which degrades the characteristics and reliability of the device.